The tkLayout-lite represents a derived SW version of tracker geometry modelling tool and tracker performance analysis tool tkLayout, which has been fully developed within the CMS collaboration at CERN. Its main aim is to study performance of a new silicon tracker, replacing the current one in a view of the Phase-2 upgrade (early 2020's). In order to utilize such broad functionality of tkLayout SW in other experiments an intensive effort has been made to prepare a light version of the original tkLayout tool. Its main feature is a full modularity, experiment independence and comprehensive documentation.

The key features of tkLayout-lite may be described as follows: a tracker geometry is generated from a set of simple configuration files (cf. GeometryManager & MainConfigHandler), defining the module types, tracker layout and material composition. Various support structures are then automatically added and services routed to build a truly realistic tracking system (c.f. Materialway). The tkLayout-lite has been programmed with flexibility in mind to provide natural support for various detector geometries and a wide spectrum of analyses to be run with given layout and study the best trade-off among many figures of merit, such as: tracking resolution, material budget, power dissipation, cost etc. The tkLayout-lite SW is easy to be used thanks to its modular structure. The individual analysis modules, so-called analyzers, are run sequentially by so-called AnalysisManager, first to analyze the data and then to visualize the obtained results in a compact & user-friendly way. The visualization is provided via html format. Several web pages are generated and included on the main web-site. They may contain various explanation texts, pictures, graphs, tables etc. (cf. RootWSite, RootWPage, etc.). Several important analyzers to be explicitely mentioned:

• AnalyzerResolution: perform track resolution studies, which mathematically make use of a parabolic approximation in a global chi2 fit technique to estimate the track parameters cov. matrix (parabolic approx. simplifies a more complex approach to circle fitting in XY; a line is being used to simplify the track fitting in s-Z)
• AnalyzerPatternReco: perform track propagation & estimation of tracker pattern recognition capabilities - makes use of error propagation technique applied to a parabolic approximation. To estimate the background level (background hits) for given tracker & accelerator a Fluka charged particles fluence map is assumed to be added to the tkLayout-lite on the input -> not included within the standard SW config files
• AnalyzerGeometry: report details about geometry layout
• AnalyzerMatBudget: report details about expected tracker material budget
• AnalyzerOccupancy: report occupancy & date rates being estimated based on built-in geometry & Fluka charged particles fluence map (assumed to be provided on the input to tkLayout-lite -> not included within the standard SW config files).

Developed at CERN by Giovanni Bianchi, Nicoletta De Maio, Stefano Martina and Stefano Mersi. tkLayout-lite version developed at CERN by Zbynek Drasal in collaboration with the tkLayout team https://github.com/tkLayout. To support an XML output, tinyXML library has been included within the project (c.f. LICENSE_TinyXML file).

The code is accessible from an official github repository: https://github.com/tkLayout or author's github repository: https://github.com/drasal/tkLayout (use clone command to make a local copy):

git clone -b masterLite https://github.com/tkLayout.git
cd tkLayout

To join the effort on code development or to try out the newest features implemented during the tkLayout-lite development, clone directly the development branch devLite from author's github repository:

git clone -b devLite  https://github.com/drasal/tkLayout.git
cd tkLayout

Generally, one needs several libraries to be linked with the tkLayout-lite: a working version of ROOT 6 (root and root-config should be in a user's path defined by ROOTSYS variable) and 2 specific BOOST libraries:

• ROOT 6 library set (follow instructions on https://root.cern.ch/downloading-root)
• boost_filesystem
• boost_regex

On CERN lxplus machine, the procedure is quite straightforward, simply run a bash shell and source the following configuration file before the compilation:

source setup_slc6.sh

On local Linux machine, the environmental variables need to be set first in a local setup.sh file:

• BOOST_LIB: BOOST libs directory
• BOOST_INCLUDE: BOOST include files directory
• BOOST_SUFFIX: Usually no suffix on local machines, mainly used by complex computer systems to identify different versions of BOOST installations
• ROOTSYS: ROOT 6 directory (root-config used by CMake to configure ROOT libs and includes for compilation is assumed to be located in ROOTSYS/bin)

and then the file has to be sourced:

source setup.sh

Compilation using CMake (don't forget to setup variables using setup.sh/setup_sl5.sh beforehand):

mkdir build     (all object files, help files, libs, ... will be kept here)
cd build
cmake ..        (generate makefile)
make install    (or write make all + make install)
make doc        (generate Doxygen-based documentation in doc directory)

make uninstall  (if cleaning needed)
rm *            (clean all content in build directory & restart if needed)

Create first a build directory in the tkLayout home directory. All make related content will be then created here. Change the working directory to build and call cmake .. command (directing CMake to the tkLayout uppermost directory so that it reads correctly the CMakeLists.txt, the main CMake configuration file). After all MakeFiles are generated by CMake, call make all (make install) to (re)compile the tkLayout-lite. Optional install will copy the executables into tkLayout/bin directory and create symbolic links in ${HOME}/bin directory. Hence, if a user adds this directory into the ${PATH} variable, the tklayout may be then executed from any directory on the system. To revert the install procedure, simply apply the uninstall option. Finally, in order to recompile the SW, run make all/make install command again.

If this is the first time that you install the tkLayout-lite, a few questions will be asked and a tkLayout configuration file, .tkgeometryrc, will be created in a $HOME directory:

1. One needs to provide the destination directory for the html output of the program, such directory needs to be writable for the user and readable for the web server.
2. The set of momentum values to be used for the simulation
3. Project name
4. Author of generated results

Doxygen documentation is generated using doc option and all the generated html files are saved in tkLayout/doc/html directory.

In order to ease the start-up with the tkLayout-lite SW, several reference geometry descriptions have been included within the SW package. They can be found in tkLayout-lite geometries directory, namely geometries/CMS (for CMS Ph2 studies) and geometries/FCC (for FCC-hh studies). Create a run directory first, choose one of the geometries, e.g. FCChh_v3.03, copy its content to the run directory and run tkLayout-lite here (using the main geometry configuration file as an input parameter):

cd tkLayout
mkdir run
cd run
mkdir geometries
cd ..
cp -r geometries/FCC/FCChh_v3.03 run/geometries 

The geometry description is defined and structured across several configuration files, one of which is the main config file, e.g. FCChh_v3.03.cfg. The other files (like material description, individual modules description etc.) are included to the main file using the directive commands @include. In addition to the main geometry configuration file, there exist also a simulation run parameters file: SimParms and file specifying general settings: .tkgeometryrc. The first one is included to the main config file by directive @include, the latter is automatically created once tkLayout-lite is run for the first time in a user's home directory (see First-time install section). The .tkgeometryrc file may be deleted, tkLayout will automatically create a new one and ask the user to redefine all of its values. This file may also be directly modified by the user, the following parameters are particularly important:

TKG_LAYOUTDIRECTORY="$userhome/tkLayout/run" -> Look for geometry layouts in this directory   
TKG_STANDARDDIRECTORY="$userhome/tkLayout/run" -> Look for standard config files in this directory (xml, config, etc.)
TKG_MOMENTA="1.0,2.0,5.0" -> Define individual values of transverse momenta in GeV/c
TKG_PROJECT="FCC-hh" -> Define a project name

To learn about the tkLayout-lite functionality, simply run tklayout with no input parameters defined. The typical configuration being used to study a tracker geometry, material budget and tracker resolution is the following:

cd run
tklayout -n 1000 -N 1000 geometries/FCChh_v3.03/FCChh_v3.03.cfg 

The parameter -n defines statistics to be simulated for geometry calculations, the parameter -N defines statistics for material or resolution calculations.

The simulation results are automatically saved in a results directory, which is either newly created or rewritten under geometry directory, e.g. geometries/FCChh_v3.03/results. Use any web browser on results/index.html file to display all results in a compact way. The content of such directory may be deleted as it's being automatically rewritten each time the tkLayout-lite SW is being run on the same geometry configuration. The way, how the web browser displays the final results depends on the cascade styles (being already predefined for the tkLayout SW). Hence, one needs to make a symbolic link to a style directory (predefined in tkLayout-lite main directory). Similarly, some general configurations (material database etc.) are predefined in config and xml directories. Make a symbolic link in a geometries directory to them.

The following tkLayout-lite functionality is currently supported:

Analysis options:
-h [ --help ]                       Display help info.
--opt-file arg                      Specify an option file to parse the 
                                    program options from (in addition to 
                                    command line).
-n [ --geometry-tracks ] arg (=100) Number of tracks for geometry 
                                    calculations.
-N [ --material-tracks ] arg (=100) Number of tracks for material & 
                                    resolution calculations.
-o [ --occupancy ]                  Report occupancy studies based on Fluka 
                                    data.
-g [ --geometry ]                   Report geometry layout.
-m [ --material ]                   Report material budget.
-p [ --patternreco ]                Report pattern recognition capabilities 
                                    in given occupancy (using Fluka data).
-r [ --resolution ]                 Report resolution studies.
-a [ --all ]                        Report all studies.
-e [ --extraction ] arg (=CMS FCC)  Extract tkLayout geometry to an XML file 
                                    to be used in CMS/FCC SW frameworks. 
                                    Supported values: CMS or FCC.
--verbosity arg (=1)                Verbosity level (Overridden by the option
                                    'quiet').
--quiet                             No output produced (Equivalent to 
                                    verbosity 0, overrides the 'verbosity' 
                                    option).
--performance                       Outputs the CPU time needed for each 
                                    computing step (Overrides the option 
                                    'quiet').

In order to study the --patternreco and --occupancy options, a Fluka charged particles fluence map has to be provided in config directory. As the --all option is meant to study all available analysis options together, the Fluka map is also required there on input.

To get the latest development version (usually still under development or being tested) one simply types:

git fetch
git checkout masterLite (or devLite)
make
make install

The developers of tkLayout-lite and tkLayout SWs tried their best to provide the same core functionality in both "flavours" of tkLayout, nevertheless not all the analysis options are the same or being implemented. The tkLayout functionality is more focused on CMS Phase 2 upgrade tracker needs, the tkLayout-lite on the other hand on FCC-hh tracker needs.